Help I think my plecos dieing!

My pleco(Jerry jr the second- dont ask) has recently started acting strange. I have had him for about a month now and has been healthy until a day ago he turned whitish gray and the next day I thought he was dead. But as I poked him a little he swam off. I had to go to church so I left him and when I returned he was floating on top, but wasnt dead. I did a water change and tht seemed to help a little i also gave him zucchini, but I haven't seen him touch it, now every so often he spazzes out swimming around in circles, upside down, and running into things until he latches onto something for a little while and then floats back up to the surface. Sometimes it seemed he was trying to swim down but he couldn't, any idea of what it is?

My tank is a ten gallon until I either can find a better one for my bearded dragon, in which i will move them to his 55 galon long or a bigger one for them. it houses two comet goldfish and Jerry. (Please excuse any spelling mistakes I'm doing this on a broken iPod)

Sadly, I returned from church tonight and found my Jerry dead, for real this time.

now, I have only recently saved the fish tank from my sisters room, so I haven't had to much experience actually keeping the fish other than my beta. Since I brought it into my room and have done research an realized keeping a fish tank requires much more than food and a filter. As soon as I can I plan on getting a kit but with school starting soon I'm busy an haven't had time, so I don't know any I that stuff :/ sorry for rambling but I always feel like I need to explain myself... Thanks for trying to help anyways

My royal pleco had the same symptoms. I did not have drift wood at first. After I did get the chance to get some and put it in he went under it go about 3weeks. He only came out at night for food. But after tht he has been fine sence. Did you have drift wood?